Subcaliber auxiliary barrel and extractor



July S, 1947. w. SUMMERBELL SUBCALIBER AUXILIARY BARREL AND EXTRACTOR Filed April 26, 1944 2 Sheets-Sheet l July 8, 1947- l w. SUMMERBELI. 2,423,471

SUBCALIBER AUXILIARY BARREL AND XTRACTOR Filed April 26, 1944 2 Sheets-Sheet 2 gmc/14M J w WILLIAM ummsRasLi., 5

Patented July 8, 1947 UNITED STATES PATENT OFFICE SUBCALIBER AUXILIARY BARREL AND EXTRACTOR (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The invention relates to subcaliber guns and has for an object to effect improvements looking to the better performance of the subcaliber ammunition and at the same time to save the major caliber tube from wear, corrosion, or fouling in any way incident to the use of the smaller caliber ammunition. This is important, since practice firing with smaller than standard ammunition must often be carried on extensively and over extended periods of time, and instruction would be greatly impaired by necessity for cleaning the larger gun frequently. There has been a deflciency in satisfactory subcaliber equipment of this kind, and particularly for the current models of 75 mm. and larger guns.

An important purpose is to enable the functioning of the standard breech block, firing mechanism and semiautomatic breech closing mechanisms with the subcaliber ammunition.

A further important aim is to accomplish effective extraction of subcaliber cartridge cases by functioning of the regular extractor mechanism.

It is one of the objects of the invention to present a subcaliber auxiliary tube and extractor which is readily applicable to different models of guns without structural modification of the latter, or tooling of any kind thereon; as well as to avoid marring surface finish.

An impelling motive prompting the evolution of the invention is the need of such equipment which may be applied without disassembly or structural modification of the gun on which it is to be used, while at the saine time attaining all the essential benefits of economy, accuracy of fire, and otherwise, as indicated.

A special end in view lis to enable rapid and eifective conversion of tank guns to smaller caliber with the above mentioned advantages.

In prior attempts to provide subcaliber adapters for large caliber guns difficulty has been experienced due to dissipation of the force developed by the propellant and it is an object of this invention to reduce such losses to a minimum.

One factor in such dissipation of force is friction of the projectile upon the subcaliber barrel.

Additional objects, advantages, and features of invention are involved in the construction, arrangement, and combination of parts involved in the embodiment of the invention, as may appear or be understood from the following description and acompanying drawings, wherein:

Figure 1 is a longitudinal vertical section of a mm. gun tube now largely in use, equipped with my invention, sections of the tube being omitted at intervals, forwardly of the chamber;

Figure 2 is a rear elevation of the breech end of a 75 mm. gun on which my invention is incorporated, and showing the extractors of the conventional breech mechanism;

Figure 3 is a section on the line 3 3 of Fig. 1;

Figure 4 is a rear elevation of the subcaliber tube alone;

Figure 5 is a fragmentary elevation of the breech end of the subcaliber tube alone;

Figure 6 is a rear view of the subcaliber ejector alone;

Figure 7 is a side View thereof;

Figure 8 is a rear elevation of the anchor block alone;

Figures 9 and 10 are, respectively, a bottom view and a side View of the anchor block.

Reference is made to Patent No. 1,393,353, Oct. 11, 1921, L. L. Driggs; and No. 1,802,727, April 28, 1931, to G. M. McCann, for an understanding of the extractor devices referred to hereinafter.

Referring more particularly to the drawings, there is illustrated a 75 mm. gun tube l0, which is unchanged from that heretofore used in so-called tank guns (by which is meant guns for mounting in the turrets of armored vehicles known as tanks) This tube includes the usual smoothbored chamber Il shaped to receive cartridge rounds and including also the shoulder l2 and rifled bore i3 (representation of the riing being omitted in the drawing). The chamber opens flush through the planiform breech face of the tube which is normal to the axis of the tube. The tube is customarily formed with external threads lll at its rear end, which are screwed into a breech ring i5. Upon the ring I5 there is mounted a breech block I6, its operating mechanism, and a ring mechanism, but as these are unchanged for operation with my invention, and are not directly connected therewith except for a contact by the extractors Il, they are not illustrated, and no detailed description thereof need be given here, only the extractors being referred to and illustrated.

A subcaliber barrel including a rifled tube 20 is shown, which has been made in conformity with a standard 37 mm. gun tube as to diameter of its chamber portion 2l and its bore portion 22. But the length is materially shortened in the present instance (particularly to enable its mounting in a tank gun in Situ in the tank), although this length may be varied as expediency may dictate,

for use in other larger caliber guns. At its rear end the material at the top of the tube is cut away horizontally to a depth of somewhat less than one-half the thickness of the chamber wall of the tube and from its butt face 23 a very short distance forwardly, leaving an upstanding transverse rectangular rib 24 near the breech of the tube, and a groove 25 beside the rib at its forward side. A jacket 2S forming part of the subcaliber barrel is shrunk on the rear part of the tube 2B, of a size exteriorly to fit the wall of the chamber II and cut away to conform to the cut away part of the tube 20 at the groove 25. From the jacket to near its forward extremity the tube 2i! is tapered to a minimum thickness. The tapering is excepted near the forward end of the tube where a cylindrical, externally threaded part 2'! is formed, on to which there is screwed an adapter ring 28, tightly fitting the subcaliber tube, and also tted to the bore of the tube Ill just beyond the forcing shoulder or cone I 2.

A lock block or anchor block 29 is set against the rear face of the tube IIJ, consisting of a planiform plate Si] having a thickness approximating that of the conventional extractors, of a length to extend horizontally across the breech face of the tube within the breech recess of the breech ring, and extending from the level of the base of the rib 24 to a distance above the opening of the chamber II. A forward block segment extension 3l is formed integrally with the plate Sil, its lower face 32 in a plane with the lower edge 0f the plate 3D and its upper side 33 conforming to the arc of the chamber II, and correspondingly slightly tapered to t into the chamber. The lower side 32 of this block is substantially planiform, and its thickness in the segment portion is somewhat greater than the longitudinal extent of the cut away part of the tube 2d adjacent the rib 24. At a distance from the inner face of the segment corresponding to the width of the groove 25 longitudinally of the tube 2E), a groove 34 is formed in the under face 32 of the block 23, to fit the rib 24,

With the block 23 thus fitted to the tube 26, the tube may be thrust forwardly in the large caliber tube I0 until the jacket 26 fits the chamber I I and the ringr 28 fits the bore or lands of the tube I0 as in Fig. 1. The extreme forward end of the r tube 20 is cylindrical and externally threaded as at 36, and screwed thereonto is an internally threaded anchor tube 35, cylindrical, and of uniform thickness throughout, its internal diameter being much greater than that of the barrel 2o. This tube 35 is extended beyond the muzzle of the tube I0, and there provided with a seat or anchor ring 31, fitted snugly to the tube 35, and in the bore of the larger gun a distance as a bushing. A set screw 38 is engaged through the ring 3'I against the tube 35, but the two may be otherwise secured together. The ring 3l is enlarged before the end of the tube I 0 to afford a shoulder 39. set against the muzzle end of the tube IIJ with an interposed gasket 55. Sockets 4I are shown in the outer face of the ring 3'I permitting application of a Spanner wrench thereto to screw the tube 35 onto the barrel tube 26.

Any desired number of support bushings 42 may be secured on the tube 35 spaced longitudinally thereon and fitting the bore of the tube I9.

When the tube 20 is assembled on the tube I, and drawn in with the block 29 snug against the breech face of the tube IIJ, the butt face 23 of the tube 2Q is set slightly to the rear of the plane the same as a bearing of good width supporting the inserted tube 20.

An extractor sleeve 45 is fitted slidably around I the relieved part 44 of the jacket 26, this sleeve conforming exteriorly somewhat to the shape and size oi the butt end portion of a cartridge case of the kind conventionally used in full caliber size in the tube Ill, but being preferably made of steel.

The sleeve @.6 is tapered externally to fit the chamber I I from the bearing part 45 of the jacket 26 to the mouth of the chamber, but is slotted on its upper side as at 4l (Figs. 6 and 7) over an angle slightly more than that included by the junctions of the lower face of the block 29 and wall of the -chamber II so that the block sets free across the slot :37. This permits the sleeve to slide rearward from a loaded forward position to a rear discharge position nearly two calibers of the tube ID from the loaded position in the instance illustrated.

The sleeve has an integral head 48 and peripheral flange G9, the head being of such shape and thickness that at full forward or loaded position ofthe sleeve it is nearly or quite in contact with the butt faces of the tube 2D and jacket 26, and the flange i9 lies spaced from the breech face of the tube I E? in the same degree as would the extractor flange or rim of the conventional cartridge case of a ful1 caliber round loaded in the larger caliber gun. The rear face of the head Y43 is planiform, and in or slightly rearward of the plane of the rear face of the block 29 when the sleeve @E is at forward or loaded position.

By reason of the size, shape, and proportions of the sleeve Q6 as thus described, it is able to function with, and be operated by, the extractors I'I of the regular breech mechanism of the larger caliber gun of which the tube I0 forms a part, It will be apparent that it would also function with other extractor mechanism or devicefor engaging conventional extractor rims on cartridges of the larger size.

The head i8 is formed with a concentric opening Eli, of the same diameter as, and alined with, the chamber 2l, and this opening is rabbeted at the rear as at 5I, to receive the usual extractor flange of the smaller caliber cartridge case when such a round is inserted in the chamber 2`I, so that the rear face of the head of the smaller cal iber case will set at or slightly to the rear of the plane of the rear face of the extractor head 48v when the parts are at full loaded position. This permits the forward face of the breech block; of the standard breech mechanism of the larger caliber weapon to set against the head of the subcaliber cartridge case when the block is operated normallythat is, by the reaction of the regular closing spring-after the breech has been opened manually by the standard operating handle forming a permanent part of the conventional breech mechanism, these features being well known and understood. 'l

Also, as a consequence of the inter-operative relation of the structure of my invention, the subcaliber ammunition, and the breech mechanism, the standardring mechanism of the larger-iA caliber gun will function conventionally with the` S subcaliber rounds, the primer of the smaller caliber cartridge being alined with the firing pin of the regular breech block when the latter is closed.

The several features pointed out obviate the need for any special mechanism whatever in order to fire subcaliber ammunition when using my invention, and the only departure from usual full caliber operation, after my subcaliber chamber and barrel are put in place, is that the breech must be opened manually, due to the lack of sufficient recoil from firing f the subcaliber ammunition.

In use, guns such as the 75 mm., and larger and smaller caliber weapons using the same type of breech closure, may be equipped with my subcaliber tube and operated as last above mentioned, and it is believed applicable to use with other breech structure, including the rotating block type.

The application of the subcaliber chamber and barrel, and firing of the subcaliber ammunition are effected without alteration of structure or use of attaching bolts or screws, welding, or other permanent means; and it is a further advantage that even marring of surface finish or deposit of explosion products on surfaces of the larger caliber weapon are avoided. The bore and chamber of the larger gun is also protected from injury by climatic conditions.

The preparation of the original weapon for subcaliber operation is accomplished within a few minutes with the weapon in situ in the eld, by merely opening the breech, inserting my tube 29 and block 29 into the chamber I I then inserting the anchor tube 35 at the muzzle and screwing it onto the tube 29 at 3B until the ring 31 and plate 30 are drawn against the muzzle and breech of the tube I0.

Thereafter, a conventional round of the smaller caliber ammunition is inserted through the opening I), the head d5 being at this time in a position withdrawn a distance by reason of the functioning of the extractors II incident to the last operation of the operating handle of the breech mechanism.

When, now, the inserted round is thrust home in the chamber ZI, or nearly so, the sleeve 46 and its head and iiange 49 are carried forwardly, the ange 49 pushing the extractors I'I forward as in their ordinary functioning with full caliber rounds. They consequently release the breech block so that the closing spring (compressed when the breech was opened) may, and does move the breech block to closed position. In this movement of the block its upper bevelled edge will cam the live round snugly into the chamber 2|, and the ring pin will move with the block into alinement with the primer of the small round and stop there. The firing mechanism having been cocked by the breech mechanism, the subcaliber round may now be red at any time by the usual manual means provided in the original mechanism.

Upon firing, the round functions normally, the projectile passing through the bore 22 with usual rotation, acceleration, and velocity values of the round in proportion to the shortened barrel, and with ample clearance in the anchor tube to avoid impairment of the ight characteristics of the projectile.

There will be a moderate recoil involving movements which will be of an extent only a small part of those produced by the full caliber ammunition for the larger gun, and the summary movement will be insufiicient to operate the breech 6 block. Consequently, after each subcaliber round is fired, it is necessary to open the breech by the usual manual means forming part of the standard equipment of the larger caliber gun.

In the breech-opening operation of the larger gun, the breech block is drawn rearwardly and downward to clear the breech of the tube 20, and at the same time the extractors Il are actuated so as to force the flange 49 and sleeve 46 rearwardly, and this is usually accomplished with suiiicient speed to throw the sleeve 49 rearwardly with considerable momentum, until stopped by striking of the forward end of the slot 41 against the segment portion of the block 29. The subcaliber cartridge case being engaged loosely through the opening y5I), this rapid movement will also cause propulsive ejection of the extracted case of the spent round so that the sleeve 46 becomes a combined extractor and ejector.

The opening and closing operations of the breech also effect cooking of the firing mechanism as before indicated so that after ejection of the empty case, the loading and firing procedure may be repeated with another live round, the closing operation being automatic in the mm. type of mechanism.

The plate 36 performs a most important function in the organization presented, and by fitting to the chamber wall on closing of the breech, largely obviates the need for strong supports or expanding wedges within the tube II). The principal purposes of the bushings 42 and ring 31 are to afford rigidity of the tubing 35 in the tube I0, to prevent rotation of the inserted parts, and to keep the tubes 29 and 35 in good alinement. That is to say, the plate 3 enables the breech block of the larger weapon, by adequate pressure on the base of the inserted subcaliber cartridge case, to press the latter and also the tube 20 forwardly to a snug t of the jacket 29 and adapter ring 28 in the chamber I I, and at the same time to position the head 48 in cooperative relation to the extractors I'I. The fact should also be appreciated that the provision of the sliding extractor and ejector on the subcaliber weapon, and the provision thereon of a head portion shaped to function with the larger caliber extractor devices, is capable of embodiment in other construction of subcaliber guns coordinated with the breech closure and firing mechanism of the larger weapon in which it is inserted.

In this respect the extractor is the most mportant feature of the invention.

The invention may be adapted to other forms of breech closures, with advantages corresponding to those evident in the particular embodiment shown, as well as others, and while I have disclosed this particular device with great particularity it will nevertheless be understood that it is purely exemplary and that various modifications of construction, arrangement and cornbination of parts, substitution of materials, and substitution of equivalents, mechanical and otherwise, may be made without departing from the spirit of the invention set forth in the appended claims, wherein I claim:

1. A subcaliber device for a large caliber gun having a chamber, bore and cartridge case extractors; comprising a barrel chambered and bored to receive conventional small caliber ammunition rounds, means to fix the barrel in the large caliber gun whereby the head of a cartridge case of a round loaded in said barrel will be in the same plane as would the head of a cartridge case of full size ammunition round loaded in the chamber of the said gun; said means comprising a transversely relieved part ofthe'p'per part only of the breech end'of the barrel extending forwardly a limited distance from the breech face f of the barrel, a transverse upwardly presented rib on said relieved part spaced below the chamber on its under side to receive said rib separably,

whereby when the barrel ifs-assembled to the said gun the plate and block and barrel are locked together and the latter is held against forward movement in the gun, means to holdr theY barrel against rearward movement in the gun, and a reciprocable member on said barrel, including a head shaped to lie against the said breech face of the gun below said plate, having a rabbeted opening to receive loosely a subcaliber roundinserted in the chamber yof the barrel, said head having also a lateral flange portion corresponding to the rim of a large caliber round or the gun,

whereby said extractors may draw said recipro' cable membery rearwardly to extract a subcal'iber cartridge from said barrel.

2. The structure of claim 1 wherein said barrelhas an vadditional exterior relieved face extending forwardly from its breechy face beyond and before the said plate and block, the relieved surface being concentric with the axis of the barrel, said reciprocable member including a forward. extension slidable over said relieved face vand to a forward position with its head in the said plane, and having at the forward part of said extension a lateral part normally spaced forwardly of the block arrangedto engage the said block after a given rearward movementy of the reciprocable member to limit withdrawal. Y

WILLIAM SUMMERBELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number yName Date 252,241 Morris Jan. 10, 1882 834,341 Tucker Oct. 30, 1906 1,191,618 Saifold July 18, 1916 1,759,772 Williams May 20, 1930 2,059,658 Sandine Nov. 3, 1936 353,231 Morris' Y ,Nov. 23, 1886 230,442 Shelton July 27, 1880 1,806,223 Samaia May 19, 1931 

